Electrophysiological techniques are being used to investigate neuronal mechanisms controlling behavior using, as a model system, the escape response of the cockroach, Periplaneta americana. Particular attention is being given to the function of the abdominal giant fibers in initiating the response; the role of reafference (input generated by the animal's own activities) in producing prolonged activity; and the time course of habituation. Microelectrode recordings are being used to determine if the giant fibers are functionally equivalent or individually specialized; the relations between sensory stimuli and giant fiber firing patterns are being quantified, and chronically-implanted electrodes are being used to correlate giant fiber activity with the behavior of intact animals. Investigations will also continue on the properties of katydid singing muscles which are of interest because of the extraordinary contraction frequencies at which they operate, up to 200 per second. One goal here is to determine the quantitative relation between contraction kinetics and the development of sarcoplasmic reticulum in muscles of varying contraction speed.